Thermoplastic polyhydroxy polyether resins have been known as phenoxy resins. As they are excellent in flexibility, impact resistance, adhesiveness, mechanical strength and the like, in the electric and electronic industrial fields, they are applied to a wide range of uses, i.e., magnetic tape binders, insulating varnish for electric machines such as motors and the like, adhesives for circuit boards, films and the like. Among them, in the fields where the safety of electric and electronic products such as prevention and retardation of a fire disaster is strongly demanded, halogenated phenoxy resins, mainly brominated phenoxy resins have been used. However, it has been known that if a material comprising a halogenated substance is used at a high temperature for a long period of time, the halogenated substance is released, which causes corrosion of wires. Further, if waste products of used electric parts and electric equipments are burned, harmful substances such as halogenated substances and the like are produced. Therefore, the direct and indirect use of a halogen has been considered to be a problem in terms of the environmental safety, and materials which can replace the halogenated substances have been studied.
Patent Publication 1 Kokai (Jpn. Unexamined Patent Publication) No. 5-93041
Patent Publication 2 Kokai No. 5-93042
Patent Publication 3 Kokai No. 2001-310939
Patent Publication 4 Kokai No. 5-295090
Patent Publication 5 Kokai No. 2001-261789
Non-patent Literature Publication 1: Written by WANG C-S, SHIEH J-Y, “Synthesis and properties of epoxy resins containing 2-(6-oxid-6H-dibenz<c,e><1,2>oxaphosphorin-6-yl)1,4-benzenediol”, Polymer (GBR) VOL. 39, NO, 23, PAGE. 5819-5826 1998
Non-patent Literature Publication 2: Written by CHO C-S, CHEN L-W, CHIU Y-S, “Novel flame retardant epoxy resins. I. Synt-hesisi, characterization and properties of aryl phosphinate epoxy ether cured with diamine.” Polymer Bulletin VOL. 41, NO. 1, PAGE. 45-52 1998
Patent Publication 1 and Patent Publication 2 propose flame-retardant films using a thermoplastic polyhydroxy polyether resin. However, all the flame retardants used therein are halogenated substances. Flame retardation using phosphorus is not described. In addition, Non-patent Literature Publication 1 describes a compound obtained by the addition reaction of a phosphorus-containing compound with benzoquinone as a flame-retardant compound using a phosphorus compound. However, it is used as a reactive flame retardant for epoxy resins which are thermocurable resins. There is no description relating to a thermoplastic resin and an insulating film. Non-patent Literature Publication 2 describes that a novel epoxy resin was obtained as a thermocurable resin using a phosphorus-containing compound, benzquinone and epichlorohydrin, but does not describe a thermoplastic resin and an insulating film.
Further, in Patent Publication 3, a phosphorus atom-containing flame-retardant thermoplastic resin was obtained, and the resin exhibited an improved heat resistance. However, the film thereof is hard and brittle and the resin exhibits selectivity of a solvent, and thus there are concerns that there may be an adverse effect that a solvent harmful to human bodies needs to be used, and the solubility thereof in a solvent must be improved. Recently, adaptability of a resin in the use where more flexibility is required, such as use of a resin for flexible laminates and the like has been demanded. In addition, in the use of a resin for adhesives, flexibility thereof at a low temperature has been demanded, and it is difficult to make conventional phenoxy resins exhibit sufficient flexibility. Patent Publication 4 and Patent Publication 5 describe a glycidyl ester type epoxy resin as one of bifunctional epoxy resins which are materials for a high molecular epoxy resin (equivalent to the “thermoplastic polyhydroxy polyether resin” of the present invention). However, there is no description relating to a characteristic of carboxylic acid-containing thermoplastic polyhydroxy polyether resins and there is no description relating to flame retardancy.